The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
A roof assembly having a closure element can be driven by a pull cable drive. Regardless of opening or closing the closure element, a steel cable is loaded by an electric motor with a pulling force only. Furthermore the driving motor is placed in the rear of the vehicle. In case the vehicle is subjected to a head on collision, occurring in such situation where the closure element of the open roof system is in its open position, the pull cable is loaded with an impact force, initiated by the kinetic energy of the closure element in its open position. This impact force may damage the pull cable, and ultimately break the cable, after which the connection between car and closure element is partly lost. A spring biased construction can be connected to the pull cable to allow, in case of a collision, the impact force to be absorbed without any damage to the pull cable.
In another structure of a roof assembly, the assembly has a closure element, slidably guided in a guide and connected with a drive unit, and equipped with a brake system, that decelerates the closure element, in a situation in which the closure element is in its open position, and the vehicle is subjected to a frontal crash.
The brake system is designed such that it breaks upon impact and thereby interrupts the connection between closure element and drive unit. Due to this breakage, the brake system is able to convert into a wedge type brake system, whereby two wedge parts slide relative to each other until this movement is stopped, due to the two parts being stuck inside the channel of the guide rail.
The solutions described above are for the purpose of the specific circumstances of a vehicle having a roof assembly, comprising a closure element and a driven element, and whereby the closure element is in its open position when a collision happens. The solutions described above are additional systems, adding weight and cost to the roof assembly and, may be in an area of the open roof system, namely the closure moving mechanism, where the packaging space is very limited. Apart from weight, cost and space the fact that the connection between closure element and drive unit is broken, leads to the risk of the closure element being separated from the car in case the remaining brake system is forced out of its guiding rail by the large deceleration forces.
The spring biased pull cable system has the disadvantage of being biased also during normal operation of opening and closing the closure element. This may cause misalignment of the closure element in situations where the closure element is facing obstructions in its operating mechanism whereby, due to the obstructions, the spring is compressed slightly, so that the closure element's position relative to the drive unit is shifted. In such situations the electronic positioning for the closure element in the drive unit does not match with the actual positioning of the closure element. This may cause serious malfunctioning problems of the roof assembly.
It is a requirement of several vehicle manufacturers that for a roof assembly with a closure element in its open position, in case of a collision, the closure element is moved a short distance in longitudinal direction only. This requirement is set to absorb the kinetic energy of the closure element in case of a collision, while keeping a full connection between closure element, drive unit and guiding rails, on the one hand, and to avoid a situation in which an object can be caught between the closure element and the aperture opening of the fixed roof, on the other hand. This is necessary due to the fact that the anti pinch detection and reversal motion of the closure element does not function in case of longitudinal movement of the closure element during a collision. The longitudinal distance required for the closure element to move during a collision is different for the various vehicle manufacturers.
Furthermore it is a requirement of vehicle manufacturers that the roof assembly, when the closure element is in its open position, its normal functions is preserved after the vehicle is subjected to what is called a city crash. This definition of city crash is used to designate light crashes, with low vehicle speeds, whereby the deceleration is below an average value of about 15 m/s2. Above this deceleration value the requirement may not be valid.